1. Field of the Invention
The present invention relates to a slice image creation device, a three-dimensional printing system, and a slice image creation method.
2. Description of the Related Art
Conventionally, a three-dimensional printing device that prints a desired three-dimensional object (hereinafter, referred to as a “target object”) is known. This type of three-dimensional printing device uses, for example, a computer-aided design device (hereinafter, referred to also as a “CAD device”) to create data on a three-dimensional model which is usable to print the target object (hereinafter, such a three-dimensional model will be referred to as a “target object model”) (see, for example, Japanese PCT National-Phase Patent Publication No. 2003-535712). The target object model is sliced at a predetermined interval to create a plurality of two-dimensional slice models corresponding to cross-sectional shapes of the target object (hereinafter, such a two-dimensional slice model will be referred to as a “target slice model”).
A target slice model is defined by a contour of the target object. The target slice model is divided into a printing region, which is to be printed, and a non-printing region, which is not to be printed, along the contour. Thus, for example, the printing region in the region of the target slice model is colored white and the non-printing region is colored black by the CAD device, so that a slice image (hereinafter, referred to as a “target slice image”), which is an image of the target slice model, is created. The slice image includes a contour that distinguishes the printing region and the non-printing region from each other.
A three-dimensional printing device includes, for example, a table provided with an opening, a tank that is located on the table and accommodates a photocurable resin, a holder that is located above the tank and is movable up and down, and an optical device that is located below the table and outputs light. Light that is output from the optical device is directed toward the photocurable resin in the tank through the opening in the table. A portion of the photocurable resin, accommodated in the tank, that is irradiated with the light is cured. The position to be irradiated with the light is controlled to appropriately change the position in the photocurable resin to be cured, so that a portion of the photocurable resin located in the region colored white (printing region), in the target slice image, is cured whereas a portion of the photocurable resin located in the region colored black (non-printing region) is not cured. As a result, a cross-sectional shape conformed to the target slice image is formed. The holder is sequentially moved up to continuously expand the resin layer downward. In this manner, a desired target object is printed.
There may be a case where the target object to be printed is a combination of a plurality of singular objects (hereinafter, referred to as “unit objects”) (such a combination will be referred to as a “whole target object”). For example, FIG. 13A is a perspective view of a target object model 170 corresponding to the whole object (hereinafter, such a target object model will be referred to as a “whole object model 170”). FIG. 13B is a side view of the whole object model 170. As shown in FIG. 13B, the whole object model 170 is defined by contours of unit object models 170a, 170b and 170c corresponding to a plurality of unit objects. FIG. 14 shows a slice model 172 obtained as a result of slicing the whole object model 170 shown in FIG. 13B at position PT100 (hereinafter, such a slice model will be referred to as a “whole slice model 172”). As shown in FIG. 14, the whole slice model 172 is defined by contours 173a, 173b and 173c of the plurality of unit object models 170a, 170b and 170c, like the whole object model 170. The whole slice model 172 may include an intersection 184, at which the plurality of contours 173a, 173b and 173c cross each other.
Before a slice image of the whole slice image 172 (hereinafter, such a slice image will be referred to as a “whole slice image”) is created, the CAD device or the like traces the contours of the whole slice image 172 to extract a contour showing the entirety of the whole slice model 172 and distinguishes a printing region and a non-printing region of the whole slice model 172 from each other, among the plurality of contours 173a, 173b and 173c (hereinafter, this process will be referred to as “peeling”). For example, in the case where the CAD device traces the contour 173a in a direction of the arrows on the contour 173a in FIG. 14, the CAD device transfers from the contour 173a to another contour at the intersection 184. However, at the intersection 184, there are a plurality of contours to which the CAD device may transfer. Specifically, at the intersection 184, there are two contours to which the CAD device may transfer, namely, the contour 173b and the contour 173c. Therefore, there is a risk that the CAD device may transfer to the contour 173b despite that the CAD device should transfer to the contour 173c. When this occurs, the CAD device does not perform the desired peeling for the whole slice model 172 correctly (“peeling” refers to acquiring a contour distinguishing a printing region and a non-printing region from each other), and thus may not create a desired whole slice image. In the case where the desired whole slice image is not created, a desired whole object is not printed. As described above, “peeling” refers to acquiring a contour distinguishing a printing region and a non-printing region from each other. The expression “perform peeling” refers to tracing such a contour distinguishing a printing region and a non-printing region from each other. In the case where the CAD device, while performing the peeling, encounters an intersection at which there are a plurality of contours to which the CAD device may transfer (e.g., intersection 184), the CAD device transfers to the contour distinguishing the next printing region and the next non-printing region after passing the intersection. This keeps on selecting a contour located on the outermost profile of the printing region.